The present invention is directed to filling the need for an improved product for removing lipid deposits from contact lenses, particularly RGP lenses, as well as providing compositions which improve the wettability and overall comfort of contact lenses.
The removal of deposits of proteins and other materials from the surfaces of contact lenses has been the subject of extensive research in the contact lens care industry since large scale introduction of contact lenses in the 1960's. Much of the research has focused on the removal of protein deposits from contact lenses. There are today a number of cleaning products on the market which remove protein deposits on contact lenses. Enzyme-containing cleaners are especially effective in this regard. Although other types of soilants on contact lenses have received somewhat less attention than proteins, such deposits can also be quite troublesome to the wearers of contact lenses. This is particularly true of lipid deposits which have become increasingly recognized as a significant problem for wearers of contact lenses, especially the lenses classified as "rigid gas-permeable" or "RGP" lenses. See, e.g., S. W. Huth and H. G. Wagner, "Identification and Removal of Deposits on Polydimethylsiloxane Silicone Elastomer Lenses", International Contact Lens Clinic, 8 (Jul.-Aug.), 19-27, 1981; D. E. Hart, "Contact Lens/Tear Film Interactions: Depositions and Coatings," In O. H. Dabezies, Jr. (Chief Editor), Contact Lenses (The CLAO Guide to Basic Science and Clinical Practice), Second Edition, Volume 2, Little, Brown and Company, Boston, 1988, pp. 45.A-1-45. A-27; R. C. Tripathi and B. J. Tripathi, "Lens Spoilage." In O. H. Dabezies, Jr. (Chief Editor), Contact Lenses (The CLAO Guide to Basic Science and Clinical Practice), Second Edition, Volume 2, Little, Brown and Company, Boston, 1988, pp. 45.1-45.33; R. M. Grohe, "Special Clinical Considerations." In E. S. Bennett and R. M. Grohe (Editors), Rigid Gas-Permeable Contact Lenses, Professional Press Books/Fairchild Publications, New York, 1986. pp. 151-174.
The use of polymeric surfactants in contact lens care products has been described in numerous publications. Reference is made to the following publications for further background concerning such usage:
U.S. Pat. No. 3,171,752 (Rankin), issued Mar. 2, 1965; PA1 U.S. Pat. No. 3,767,788 (Rankin), issued Oct. 23, 1973; PA1 U.S. Pat. No. 4,048,122 (Sibley, et at.), issued Sep. 13, 1977; PA1 U.S. Pat. No. 4,493,783 (Su, et al.), issued Jan. 15, 1985; and PA1 U.S. Pat. No. 4,808,239 (Schafer, et at.), issued Feb. 28, 1989. PA1 viscosity 20 cSt; refractive index 1.4416, specific gravity 1.007, melting point 0.degree. C., surface tension 23.6 dynes/cm.
In addition, various types of contact lens care products containing surfactants have been marketed in the United States and other countries. Those skilled in the art of contact lens care products will be generally familiar with such products, which include Lobob Daily Cleaner, Lobob Laboratories, San Jose, Calif.; LC-65, Allergan, Irvine, Calif.; Titan II, Barnes-Hind Pharmaceuticals, Inc., Sunnyvale, Calif.; and Opti-Clean.RTM., Alcon Laboratories, Inc., Fort Worth, Tex., for example. The above-cited patent issued to Sibley, et at. is believed to relate to the Titan II product, which has been marketed by Barnes-Hind. The patent issued to Su, et at., relates to the Opti-Clean.RTM. product.
Notwithstanding such surfactant containing products, there remains a need for improved products capable of achieving even greater cleaning of contact lenses. In view of the significant worldwide market for rigid gas-permeable (RGP) lenses, there is a particular need for products which are more effective in cleaning these lenses. RGP lenses are generally less susceptible to formation of protein deposits than are soft (hydrogel) contact lenses, especially those categorized as ionic, high-water-content lenses. However, RGP lenses are susceptible to formation of lipid deposits. Therefore, the removal of lipid deposits is today a principal focus of research in the area of cleaning products for RGP lenses. The need for a product which effectively removes lipid deposits from these lenses was a principal impetus for the present invention.
A further motivation for the present invention was the need for a product which is generally effective in removing lipid deposits from all types of contact lenses, as well as enhancing the wettability of contact lenses. While other factors also contribute to lens-wear comfort, the wettability of a contact lens (i.e., the ability of the lens to become wetted with tear fluid which normally hydrates and lubricates the cornea upon blinking of the eye) is a critical factor with respect to the comfort of the lens when placed on the cornea. It is therefore highly desirable to treat the surface of contact lenses with a composition that enhances the wettability of the lenses while being worn. This is particularly true with RGP lenses and other types of lenses having a lower water content than soft, hydrogel type lenses.